Automotive vehicles are commonly equipped with an AM/FM radio for providing audio entertainment for the passenger(s) in the vehicle. Audio car radios are typically packaged with playback devices such as compact disc (CD) and/or tape cassette players, as well as other audio entertainment devices. AM/FM radios include AM and FM receivers for receiving amplitude modulated (AM) and frequency modulated (FM) signals, respectively. Also included is a tuner for adjustably selecting amongst a plurality of radio wave signal channels that are generally available on the commercial airwaves. Many AM/FM radios are programmable to set desired radio wave channels (frequencies), so that a user may select a preset channel. In addition, conventional AM/FM radios are commonly equipped with channel seek and scan operations which enables the radio to successively search out those available radio wave channels meeting a minimal signal strength requirement.
The radio seek operation is performed when a user depresses a seek pushbutton. In response to depressing the seek pushbutton, the radio scans each successive signal channel, in increasing or decreasing order of the frequency bandwidth, and selects the next received signal channel having a signal strength greater than a seek sensitivity threshold. Each depression of the seek pushbutton will tune to the next received signal channel having a signal strength exceeding the seek sensitivity threshold. The scan operation automatically repeats the seek function at set time intervals. The seek sensitivity threshold is commonly fixed by the manufacturer of the radio during a one-time seek sensitivity alignment procedure.
Automotive radios employing the fixed seek sensitivity threshold may be well suited for some users. However, a fixed seek sensitivity threshold has several drawbacks in that, as the vehicle moves into different geographic regions, the available number of signal channels and the strength of the radio wave signals may change. The signal strength of radio wave signals can change dramatically, and some stations may disappear altogether, while other stations become available. This is especially true when the geographic position of the radio receiver changes in excess of fifty miles. Further, the fixed seek sensitivity threshold may not be adequate for use in certain geographic regions, in which the vehicle be employed. For example, a seek sensitivity threshold that is sufficient for use in urban regions may be insufficient for use in rural regions where the threshold value may result in the reception of too few stations during a seek operation. Contrarily, a lower seek sensitivity threshold that is sufficient for use in rural regions with fewer available stations may result in the selection of too many signal channels when used in an urban region.
The decision as to what level of signal strength is listenable is subjective, and may vary based on the concentration of receivable radio station signals available within the region of use. In areas of few radio stations, listeners may accept a lower seek sensitivity threshold, and thus noisier signals, than listeners located in a region with a higher number of radio stations. Accordingly, it is therefore desirable to provide for a tuneable automotive radio that provides a seek operation to enable a user to select an adequate number of signal channels.